Project 1: Focal ischemia affects gene expression in brain, and such gene expression affects outcome. Neuroprotective genes are induced by premonitory sublethal focal ischernia resulting in tolerance. Ischemic tolerance also results from sublethal stress caused by global ischemia and by systemic endotoxin priming. Our goal is to discover the subset of genesthat produce tolerance in each of these paradigms. Our previous approach to gene modulation in brain ischenaia was subtractive hybridization and cloning. We cloned 27 new genes over the past five years. We will now use microarray technology to increase our capabilities for gene discovery and focus the efforts on protective genes modeled in ischemic tolerance. We have developed new mouse models of tolerance in order to use murine gene chips and exploit the power of the mouse genome. Our approach is to use several models, each of which results in tolerance but with distinct stimuli or regional targets in brain. We will characterize tolerance to focal ischemia in cortex protected by prior brief focal ischemia or endotoxin priming, and will characterize tolerance to global ischemia in CA 1 neurons protected by prior brief global ischemia. Multiple models and replicates will permit sophisticated statistical analysis of data. Established core facilities for genomics will enable optimal data management and analysis. New informatics and data mining collaborators at Pacific Northwest National Laboratories Supercomputer and Bioinformatics divisions adds substantial strength to our data analysis capabilities. Our goal is to find endogenous pathways of neuroprotection modeled in tolerance. To this end we will identify genes and pathways regulated during tolerance by preconditioning focal ischemia (Aim 1); identify genes and pathways regulated during tolerance by endotoxin priming (Aim 2); and identify genes and pathways regulated during tolerance in the selectively vulnerable neurons of the CA 1 sector following global ischemia (Aim 3). Genes of known and unknown function discovered in these tolerance models will be advanced to projects two and three for validation in in vitro and in vivo systems based on a specific strategic plan.The elucidation of endogenous protective systems should identify novel approaches for stroke treatment.